If most peasants in the medieval ages were structurally poor due to relying on subsistence farming; how could most landowning nobles become wealthy, if most taxes were only paid in produce? How could they afford to buy expensive equipment or even have their own military retinues?
3Documenting preliminary research will improve both the probability of an answer and the quality of the answer(s) Also, queston is far too broad. An answer would require a survey of the entire globe over thousands or tens of thousands of years. Plus a definition of "noble". Question assumes that nobles were wealthy, which for much of history is patently untrue.– MCW ♦Oct 4, 2022 at 16:55
The Doomsday Book makes clear that in England, by the time of the Conquest, not only is there considerable economic surplus but many of the peasants were far from subsistence farmers.
The peasant tenantry can be broadly subdivided into two main groups:
- Free peasants: freemen & sokemen. They formed about 12% of the population recorded in the Domesday Book.
- Unfree peasants: villeins, bordars and cottars. According to the UK National Archives website, These groups made up about 72% of the population recorded in Domesday. The Lord of the Manor could move them between estates as he wished, and also had the power to approve or prevent marriages.
Slaves: comprised roughly 10% of the population recorded in the Domesday Book. This group had no property rights, and are not included in the peasant tenantry. They could be bought and sold at will by their lords.
Villeins were both the wealthiest, and the most numerous of the unfree peasants. They made up about 40% of the population recorded in Domesday, and often held fairly substantial portions of land (up to 40 acres is recorded in some instances).
Certainly cottars were subsistence farmers; but it's by no means certain that bordars were as well. Villeins and freemen, comprising over half the adult male population, were most definitely NOT subsistence farmers.